Silphium asperrimum Hooker. Phen: May-Oct. Hab: Prairies and woodlands. Dist: N. GA, TN, and MO south to AL and LA.
Origin/Endemic status: Endemic
Taxonomy Comments: There has been confusion as to which entity the name Silphium asperrimum is best applied. Perry (1937) interpreted the name S. asperrimum as a synonym of the western S. radula, and therefore assigned the eastern entity to the next available name Silphium gatesii. However, the type specimen of S. asperrimum is collected from east of the Mississippi River (vicinity of Covington, Louisiana), a region to which S. radula is unknown, and it appears to have the small heads and reduced ray flowers typical of the eastern entity. The name S. asperrimum is therefore best applied to the eastern entity. Nomenclatural issues aside, Silphium asperrimum appears morphologically close to Silphium radula and likely intergrades near their region of contact.
Synonymy: ~ Silphium asperrimum Hook., misapplied by Cronquist (1949); > Silphium asperrimum Hook. – Tx, Perry (1937); < Silphium asteriscus L. – F, G, W; < Silphium asteriscus L. var. asteriscus – C, FNA21, K3, K4; ~ Silphium dentatum Elliott var. gatesii (Mohr) H.E.Ahles; > Silphium gatesii C.Mohr – Tn, Perry (1937); < Silphium integrifolium var. asperrimum (Hook.) B.L.Turner; ~ Silphium radula Nutt., misapplied by Cronquist (1980), Jones & Coile (1988), and Weakley (2015); < Silphium radula Nutt. – K1